There are two options at this point.

The first option is to extend your year end to Sep 30, 2024 and manually adjust the Retained Earnings when you need to print a balance sheet.  You can manually post a year end but you need to do this on Oct 1 using the numbers from Sep 30.

The second option is to fix it through a data repair process.  There are a few people that can do it and it does cost for the service.  When I do this, I add a note to the entries to indicate what changed.  Once done, the year end is changed and the entries originally entered after Sep will still be dated after Sep in the next fiscal year.